Dispersion of Nonlinear Optical Susceptibilities in Hexagonal II-VI Semiconductors

We have determined the dispersion of three independent nonlinear optical susceptibilities, |d₁₅|, |d₃₁|, and |d₃₃|, for CdS and CdSe. Tunable dye lasers (0.73 to 1.0 {μ}m) were used. In spite of the large absorption at the second harmonic and/or fundamental wavelengths, Kleinman's relation (d₁₅=d₃₁) holds. The ratio |d₃₃d₃₁| exhibits dispersion and deviates from Robinson's relation (ratio of 2). The relative phase angles between d₁₅ and d₃₁ and between d₃₁ and d₃₃ were measured at two wavelengths by a new reflection interference technique.